Electrical connection



A. CHURCHWARD.

ELECTRICAL CONNECTION.

APPLICATION FILED JUNE I9, 1920.

1,403,231, Patented Jan. 10,1922,

UNE'FED STATES,

PATENT OFFFCE.

ALEXANDER CHURCHWARD, OF NEW YORK, N. Y., ASSIG-NOR TO Wilson WELDER &

METALS CO., INC, OF BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

ELECTRICAL CONNECTION.

To all whom it may concern.

Be it known that I, ALEXANDER CH RCH- WARD, a citizen of the United States, residing in the borough of Manhattan, city, county, and State of New York, have invented certain new and useful Improvements in Electrical Connections, of which the following is a specification.

This invention relates to improvements in means for joining electrical conductors and more particularly to means for coupling a high resistance rheostat unit to a low resistance conducting wire leading to an electrical circuit.

One object of this invention is to produce an electrical. juncture connecting two terminals of widely dissimilar resistances which will have a low contact resistance and in which substantially all of the heat generated by the rheostat will be liberated in the rheostat-elements and the heat generated at the juncture itself will be reduced to the minimum so that the terminals will remain comparatively cool. This'construction prevents premature deterioration of the terminals and hence increases the efliciency, economy and durability of the rheostat.

Another object is to construct an electrical connection between terminals of widely variant conductances by coating the terminal having the higher resistance with a metal of a lower resistance preferably similar to that of the low resistance terminal so that the contacting metals at the joint will be similar andof substantially the same resistance. It has been discovered that with such a joint the heating effect which occurs at the juncture of two dissimilar metals is practically avoided. The utilization of this phenomenon in practice results in immense saving of power and material. This is specially true when applied to joints which are adapted to work loose. In fact it has been discovered that even with a joint loose enough to be completely burned out at a red heat 1n the old form of construction, applicants oint will remain cool and will not deteriorate.

These and other objects of myinvent on are set forth in the following description and claims, and illustrated in nying drawings in which: a

igure 1 is a view partly in section, illustrating one embodimentof my improyed electrical connection shown in its operating position on a panel.

Specification of Letters Patent.

- copper 17 the accompa surfaces of t Patented Jan. 18, 1922. 390,238.

Figure 2 is a perspective View showing the improved connection disconnected from the remainder of the rheostat.

Referring to the drawing, the numeral 10 represents a welding panel or board preferably of transite or other similar insulating material. 2

The welding panel 10 is provided with a circular opening 11 through which passes the round-headed bolt 12 preferably of brass. Connected to the end of said bolt 12 adjacent the bolt head 12 is the terminal 13 of the rheostat unit, and at the other end is the conductor or lead 1 1 of copper, or the like, the latter being preferably covered with the asbestos coating 15.

The rheostat unit 13 comprises a strip of high resistance metal such as nichrome provided with flanges 16 upon its side edges and with the flattened end portion 17.- The end of the terminal 13 is provided with a central perforation fitting about the bolt 12 and has on both of its faces a coating of preferably deposited by electroplating.

The deposit of metal upon the terminal of the nichrome strip should be confined to the flattened portion 17 at the extreme end so that the coating will not in any way interfere with the resistance of the rheostat unit.

The washers 18 and 19 also preferably of brass are arranged on the bolt 12 in contact with the opposite faces of the flattened end 17 of the rheostat terminal 13, and are held tightly in contact therewith by means of the brass nut 20 threaded upon said bolt. and bearing upon the steel lock washer 21.

Located upon the other side of the nut 20 are the brass spacing washer 22 and the insulating tube 23 preferably of porcelain bearing upon the welding panel 1.0. Upon the other side of the panel 10, the lead 14 is connected to the brassbolt 12 by'means of the brass washers 24, 25 and 26, the brass r'ovided with a slot owing ready adjust- )ressure upon the contacting e terminals by means of a screw-driver,

In operation the coating de osited upon the opposm surfaces of the fia tened tel-mi nal of the high resistance element will result in reducing the heat generated at the terminal to the minimum, for any given pressure existing between the contacting surfaces.

It will therefore be obvious that according to the present invention a slight loosening at the joint of the rheostat terminal is less serious than was formerly the case. "Hence a rheotsat is more nearly fool proof and can be operated with a cheaper grade of labor with practically no danger of burning out of the rheostatv elements which would formerly have occurred when the binding screws came loose.

The metal coating l7 may be applied to the nichrome strip otherwise than by electrodeposition, as by welding or hot rolling under pressure. In any case however, the metal of the coating must enter the pores and interstices of the nichrome strip and be practically completely integrated therewith. There is thus no possibility of any air-gaps existing between the nichrome. and its coating and hence the heat generated at this surface is reduced to the minimum.

It has been found from actual tests with a copper plated nichrome strip that the con tact resistance of the joint was reduced in some instances by more than four times. In other words, the contact resistance from brass to copper plated nichrome was onequarter of the contact resistance from brass to nichrome without any coating. Hence, the heat which isdeveloped at the brasscopper plated nichrome joint is one-quarter of the heatgenerated between the brass-uncoated nichrome joint. i

Another important advantage of the present construction of high resistance terminal is the reduction of oxidation and scale formation at thecontact surfaces.

In carrying out my invention I doii fnot desire to be limited to the precise embodi- Inent disclosed herein, but desire it to be understood that many variations may be made within the general scope of the invention.

I claim:

1. An electrical connection comprising conductors in electrical contact with one another, one of said conductors consisting of an element of high electrical resistance having a metal coating of an element of lower electrical resistance and the other of said conductors consisting of an element of low.

electrical resistance.

2. An. electrical connection comprising two conducting elements in electrical contact with one another, one of said elements consisting of a metal of low conductivity having a coating of a metal of higher conductivity and the other of said conductors consisting of a metal of high conductivity.

3. An electrical connectionfor conductors comprlsing conductors in electrical. contact with one another, one of said conductors a metal of lower electrical resistance and the other of said conductors consisting of a metal of low electrical resistance.

4. An electrical connection of the class described comprising electrical conductors in contact with one another, one of said conductors composed of nichrome,i and being coated with copper, and the other of said conductors composed of brass.

5. An electrical connection of the class described comprising electrical conductors in contact with one another, one of said conductors composed of nichrome ribbon electroplated with copper and the other of said conductors composed of brass.

6. An electrical connection comprising conductors in electrical contact with one another, one of said conductors consisting ot an element of high electrical resistance having a coating of an element of lower electrical resistance, the other of said conductors consisting of an element of low electrical resistance, and means to retain said conductors in close contact with one another under pressure.

7 An electrical connection comprising two conductors in electrical contact with one another, one of said conductors consisting of an element-of high electrical resistance having a coating of an element of lower electrical resistance and the other of said conductors consisting of an element of low electrical resistance, and means to adjustably retain said conductors in close contact with one another, under pressure.

8. An electrical connection comprising two elements of conducting material in electrical contact with one another, one of said elements consisting of material of high electrical resistance having its terminal coated with an element of lower electrical resistance and the other of said elements consisting of an element of low electrical resistance, said element of high resistance being in the shape of a ribbon.

' 9. In an electrical connection of the class described, a nichrome ribbon resistance element having its terminal perforated and coated with a material of low resistance, a binding screw extending through the pertorations in said terminal, washers on said binding screw in contact with the opposite sides of the end of the terminal of said ribbon and means upon said binding screw to hold said washers in close contact with the surfaces of said ribbon.

10. A resistance element for a rheostat comprising a flat ribbon of nichrome alloy,

said ribbon having its terminal perforated coated surface of said nichrome ribbon, said binding screw extending through an insulating panel, means for holding said washers in-close contact with said ribbon, and a lead connected to the opposite end of said binding screw.

11. A resistance element having its terminal coated with a metal of lower resistance.

. 12. A resistance element of low conductivity having its terminal coatod'With a material of hi h conductivity.

13. An efectrical connection comprising two dissimilar conductors clamped together,

the conductor of higher specific reslstance being provided with a coating of a material having high electrical conductivity, said coating being molecularly integral therewith to lessen the resistance of the connection;

14. In an electrical connection, the combination with an electrical conductor, of a second conductor of dissimilar material from r the first conductoradapted to beheld in clamp ng engagement with said first conductor, the first mentioned conductor bein of less conductivity and provided with an integral surface portion of better conductivity than said first conductor and-extending over the contact surface .thereof.

15. In an electrical connection, the combination with an electrical conductor, of a second conductor'having a lower specific resistance than the first conductor, and means for clamping said conductors in contact, the first conductor-having a coating of better conductivity made integral therewith b *its entrance into the pores or interstices 0% the first mentioned conductor, said coating extending cluctor.

16. In an electrical connection, a nichrome conductor and a metal of higher conducti vity adapted to contact therewith,the nichrome conductor having an inte ral copper coating extending over'the sur ace of the nichrome which is adapted to contact with the metal of higher conductivit In testimon whereof, I have afiixed my signature to t is specification.

ALEXANDER CHUROHWABD.

over the contact surface of its con- 

